Which one of the following organs in the human body is most affected due to shortage of oxygen?

$P$ nerve fibers transmit impulses from tissues/organs to the $CNS$ and $Q$ nerve fibers transmit regulatory impulses from the $CNS$ to the concerned peripheral tissues/organs.
$\quad\quad\quad P\quad\quad\quad Q$

$P$ - Contains unmyelinated nerve fibers.
$Q$ - Contains myelinated nerve fibers.
$I$ - Spinal nerves
$II$ - Autonomic neural system
$III$ - Somatic nerve fibers
$IV$ - Cranial nerves
Select the correct option for $P$ and $Q$.
$\quad\quad P$ $\quad$ $\quad$ $Q$

Which system is responsible for the conservation of energy?

Which of the following statements is incorrect?

Parasympathetic nerves increase the mobility in